Toothpaste formulations generally contain dentally acceptable abrasive, humectant, water, and water-soluble polymer which serves as a thickener and binder for the ingredients. A variety of other ingredients such as flavors, sweeteners, preservatives and fluoride are also utilized at low levels. Glycerol and sorbitol (usually as an aqueous solution) are the most commonly used humectants for toothpaste, and depending on the characteristics desired in the product, polyethylene glycol or propylene glycol may be incorporated as well. Two types of toothpaste are widely produced: 1) cream or opaque; and 2) transparent or translucent gel.
The most commonly used thickeners or binders for toothpaste are carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), silica and magnesium aluminum silicate. Carrageenan, xanthan and polyacrylates are also used, but much less widely.
In the manufacturing process for toothpastes, incorporation of the dry water-soluble binder polymer into the composition often presents difficulties because of the tendency for lump formation when the dry polymers are added to and dispersed in aqueous systems. This increases the time required to obtain uniform hydration or dispersion of the binder polymer. Consequently, there is a need in the industry for methods of incorporating water-soluble binder polymers which lead to lump-free products, rapid viscosity development and reduced batch preparation time, and which allow convenient handling of the binder.
Japanese Patent Application No. 73036167 B discloses a composition comprising (1) carboxymethyl cellulose, alginic acid, polyacrylic acid, or a salt thereof, treated by (a) coating with glycerol or alcohol, or (b) coating with starch paste, shellac, gelatin and agar, followed by treatment (a), or (c) coating with a mixture of substances in (a) and substances in (b); (2) alkali carbonate, bicarbonate, phosphate, polyphosphate or alkali salt of EDTA, optionally treated by the methods of (a), (b) and (c); and optionally (3) glucose, sugar, fructose, maltose, mannitol and common salt. When water is added to the composition, it is rapidly wetted and dispersed, and solutions of alginic acid, polyacrylic acid or carboxymethyl cellulose can be obtained rapidly.
Japanese Patent Application No. 72044335 B teaches improving the solubility of a water-soluble polymer by coating it with molten polyhydric alcohol, sugar or emulsion aid. The water-soluble polymers include methyl cellulose, CMC, polyvinyl alcohol, alginic acid salts, polyacrylic acid or its salts, and polyacrylamide. The polyhydric alcohols include sorbitol, mannitol, inositol, and sugars include glucose, sucrose and lactose. The coating substance is used in the amount of 0.5 to 10 wt. %, preferably 3 to 5 wt. % relative to the polymer.
U.S. Pat. No. 3,850,838 to Guckenberger et al. discloses methods for preparing alcohol insoluble hydrocolloids ion the form of readily dispersible and soluble agglomerates, the process comprising intimately combining the hydrocolloid with a carbohydrate binder that is soluble in both water and alcohol and an aqueous alcoholic solvent for the carbohydrate, granulating the resulting mixture, and then drying the resulting agglomerated granules.
None of the above patents teach the use of polyol-agglomerated water-soluble or water-swellable polymer in toothpaste compositions.